Such safety armatures are used in process systems in order to bring devices in the process control system into a nonhazardous state in an emergency, for example in the event of failure of controlled armatures. In accordance with regulations, such safety armatures are only moved in an emergency. States which impede or prevent the movement of a safety armature are therefore regularly not directly detected.
In order to test whether a safety armature can move out of the permanent position at least up to a specific point in an unrestricted manner, the so-called partial stroke test is known from U.S. Pat. No. 6,435,022 B1. In this case, a safety armature is moved in a subsection of its working range, by means of which it is proven, at the instant of testing, that some of the hazardous faults which cannot be detected and which impede or prevent the movement of a safety armature are not present.
WO 01/59346 A1 has disclosed a test device for implementing the partial stroke testing which has a pushbutton, on whose actuation or by means of remote control the testing is initiated.
In this case there is the problem that the undetermined time of the testing disrupts the controlled process sequence. This is the case, for example, if in the case of a safety armature closing in an emergency, the testing takes place at the moment at which an exceptionally high quantity of the medium separated from the safety armature in an emergency is required for the process. Restricting the partial stroke to an actuating range of the safety armature by a process impediment being ruled out would restrict the significance of the testing. In the case of a safety armature which opens in an emergency, the testing could be implemented at a time at which the container which is deaerated or aerated by the safety armature in an emergency should not be opened. Deaerating applications include, for example, superatmospheric pressure armatures, and aerating applications include, for example, protective gas armatures.